Here we have an extremely high poly mesh that is, in fact, a bed of small
pebbles. I have sculpted it in Mudbox.

If we double click on the mesh in polygon mode (3),
we will see it has 102400 polys.

Switch to top view (Numpad 1) and with the cube
primitive tool selected, draw out a poly plane that just covers the bed.

Make sure the plane is completely under the high poly bed and there are no
intersecting vertices.

Give the low poly plane a material and add an image map to the material
group.

Select ‘New Map’ and choose a location, name and
file format. I chose PNG because it is lossless. We do not need alpha channel,
so choose RGB. Doing so will assign a colour to the map, but we need not be
bothered about that. It will be overwritten shortly.

Change the effect to Normal.

From a side view, measure the height difference between the high poly and the
low poly geometry with the Dimension Tool.

Right click on the image name and choose ‘Bake from
Object to Texture’.

Choose a distance that is safely larger than what we measured.

Modo will bake the normal map on that texture.

Now, hide the high poly bed and just look at the low poly plane with normal
map in Advanced OpenGL view! The result looks just like the high-poly mesh!

After adding the diffuse texture:

This is how it looks without the normal map.

And this is how it looks with the normal map.

And this is the high poly mesh.

Evidently, though the low poly plane with diffuse texture only is totally
unusable, we can easily get away with the normal mapped version if the object is
not too close and viewing angle is steep.

IMPORTANT: Though Modo baked the normals on your
chosen map, the bake information is only stored in primary memory. To store it
actually into the image file, go to FILE > SAVE ALL.

That concludes the tip. I hope it was informative. For questions and/or
comments, please write me to [email protected]